Aging is a phenotype reflected in intact organisms. It results from functional changes that occur at the cellular and molecular levels of the organism. The long-term objective of this application is to better understand the molecular mechanisms underlying human aging. The specific goal for this project is to investigate functional role of MEG3, a maternally imprinted gene, in p53 regulation and cellular senescence. Cellular senescence is a state of permanent cell cycle arrest in response to many stress signals, which has been implicated to play a critical role in mammalian aging. One specific aim of this application is to determine whether MEGS is causally involved in regulating cellular senescence in human tumor cells. A Tet-on expression system will be used to establish stable clones in a human tumor cell line with regulatable MEG3 expression. Whether MEG3 induction induces cellular senescence phenotypes will be examined. In addition, RNA interference techniques will be used to knock down p53 expression in the established MEG3 clones and whether MEG3 causes senescence in the absence of p53 will be examined. Strong evidence has indicated that MEG3 functions as a non-coding RNA. How MEG3 activates p53 presents a novel mechanism for p53 activation. Therefore, another specific aim is to determine how MEGS activates p53. Whether MEG3 RNA activates p53 through repression of Mdm2 expression will be the focus of investigation. [unreadable] [unreadable] [unreadable] [unreadable]